Did Ambien kill four Air Force special operators returning from a classified five-hour spy-plane mission in February?

The four – two special-ops pilots and two sensor operators – were aboard a perfectly-functioning Air Force aircraft as it prepared for a night-time landing at Ambouli International Airport in Djibouti, Africa.

— Seven seconds before the crash, the U-28 spy plane was 1,600 feet above the ground and diving at 5,400 feet per minute. Its Enhanced Ground Proximity Warning System blared “Sink Rate, Sink Rate” into the crew’s headsets. But the two pilots apparently did nothing.

— Three seconds later, the plane was at 1,100 feet and diving at 8,000 feet per minute. The ground proximity warning system again warned the crew: “Pull up. Pull up.” Again, the crew did nothing.

— Four seconds later, the plane crashed five miles southwest of the Djibouti airport, diving at 11,752 feet – nearly two miles — per minute.

“All four aircrew members,” an Air Force investigation into the crash released last week said, “died instantly upon impact.”

Air Force

The fatal dive, including the audible warnings to the crew.

How could this happen?

Here is the official conclusion of the investigation, led by Air Force Brigadier General Timothy Leahy:

The MC [mishap crew] never lost control of the aircraft; there are no indications of mechanical malfunction; and there are no indications the crew took any actions to control or arrest the descent rate and nose down attitude. I find that the clear and convincing evidence indicates the cause of the mishap was unrecognized spatial disorientation.

Well, OK. But how did the “unrecognized spatial disorientation” — meaning the two highly-trained pilots, with more than 3,500 flight hours between them (and more than half of that flown on combat missions) had no idea where they were — happen?

The investigation lists several possible factors, but these two are among the most intriguing:

— The pilot – the one that the Air Force believes was in control of the aircraft – had been given Ambien the day before the doomed mission, and apparently had taken one the night before the flight. The FDA says Ambien can cause a wide range of side effects, among them “confusion…decreased cognition…[and] difficulty concentrating.”

— His co-pilot, on the first mission of his deployment, had arrived in Africa 48 hours earlier from nine time zones away. The Air Force concluded he could have been suffering from “acute fatigue” that “could have delayed a necessary response in a situation where a time-critical decision had to be made.”

Such are the complications of the U.S. military’s around-the-world, around-the-clock, war on terror. “At the time of the mishap, the 34 ESOS [Expeditionary Special Operations Squadron] was running operations 24 hours a day, seven days a week,” the crash investigation noted. “The operations tempo was robust with 16 sorties spread out over every 24 hour period.” On Friday, the Washington Postdetailed the increasing activity at this isolated outpost, known as Camp Lemonnier, in the Horn of Africa.

The Swiss-built U-28 is a $14.5 million single-engine turboprop aircraft based on the civilian Pilatus PC-12. It provides intelligence, surveillance and reconnaissance capabilities in support of special operations forces. The February crash was the first among the 20-plane fleet.

More than 2,000 people gathered to honor them in a memorial service at Hulburt Field, Fla., home of Air Force Special Operations Command, 10 days after the accident. “Today we grieve, tomorrow we take to the skies and soar,” said Colonel Jeffrey Kruse, commander of the 361st Intelligence, Surveillance and Reconnaissance Group. “Today we feel loss, but because of Ratchet 33, tomorrow, instead of loss, we have the promise of victory.”

The crash investigators’ evidence was sparse: “With no eyewitness accounts, surviving aircrew members, emergency radio calls or `black box’ recordings, the specific reason for the spatial disorientation cannot be determined,” the investigation said. The only personnel who participated in the pre-flight briefing were the four men who perished.

Air Force

An aerial view of the crash site, circled in red.

War is a challenging business, and the alignment of seemingly insignificant facts can lead to disaster. That’s what happened to Ratchet 33.

Pilot Hall was at the controls, because it was co-pilot’s Whitlock’s first mission of his deployment:

The leadership [of the 34 ESOS] identified fatigue as a potential issue due to the 24/7 operations tempo of the deployed unit…The leadership also implemented a policy in which on the first sortie of the deployment, the new pilot will observe the take-off and landing and not perform them.

So just how rested was Hall? According to the crash report:

— The MC was afforded adequate crew rest in the time leading up to the accident. However, on the day prior to the incident, there was an exercise scenario at the deployed location.

Announcements regarding this exercise were broadcast to the base utilizing a loudspeaker system. One of the speakers for the system was located near the sleeping quarters of the aircrew. A lost sleep list was initiated by the MP [mishap pilot] to document any crew members in the squadron that had their sleep interrupted by the exercise announcements.

Only one member of the MC, the MOP1 [Mishap Operator #1, Wilkens] was included on the lost sleep list, although his roommate reported that he appeared to have slept well.

Even though the MP did not put his name on the list, he mentioned that the exercise announcements did affect his sleep. The ORM [Operational Risk Management] worksheet, a risk management tool that was filled out by the MC prior to the flight, showed that the MC determined that the risk stemming from preflight fatigue was low.

— The MP had recently been given additional duties as a mission commander. Along with this came a shift to a later [flight-scheduling] block. This allowed the MP to attend meetings that came along with his additional duties.

— The MP had recently had a change in his duty schedule where he advanced his duty day almost 12 hours. He was given 2 days off from the flying schedule to adjust to this new schedule. The day prior to the mishap, the MP was issued four zolpidem (Ambien) tablets. Ambien is a medication that is approved for use in aviators as an adjunct to the aircrew fatigue management program.

In other words, the night before Hall’s final flight, his sleep had been disrupted by loudspeaker announcements. He had shifted his flying schedule by 12 hours shortly before the doomed mission. To cope with the shift change, the Air Force gave him Ambien the day before the crash. While the report doesn’t say that Ambien showed up in standard post-crash toxicological testing, the investigation noted that there was “no evidence of unapproved medication use.” Ambien, given to Hall by the Air Force, was by definition an approved medication.

So if Hall were groggy at the end of a five-hour mission, how alert was his co-pilot?

Notes the report:

The MCP [mishap co-pilot, Whitlock] and MOP1 had just arrived at the deployed location 2 days prior to the mishap and had shifted 9 hours ahead during that timeframe. These changes in the circadian rhythm of these three members of the MC could have led to them suffering from acute fatigue. While this was not likely incapacitating, it is possible that fatigue could have delayed a necessary response in a situation where a time-critical decision had to be made.

These factors and others combined in deadly fashion.

The U-28, sent west of the Djibouti airfield because of other air traffic, flew over a desolate region known as a “black hole” because of its lack of “cultural lighting,” compounded by a lack of moonlight. Wearing night-vision goggles, standard on such a mission (the pair had flown more than 1,400 hours with NVGs), “could have caused the MC to have a false perception of their altitude, attitude and descent rate.”

That false perception, the investigation said, may have led the crew to ignore the two audible warnings in their flight’s final moments. While they could have checked their instruments to confirm their perception, the report said they apparently failed to do so.

If they had pulled up within two seconds of that final warning, they would have cleared the ground by 100 feet.